class_docstr: A graph consists of connected Blocks, or Heads.
  
  # Arguments
      inputs: A list of input node(s) for the Graph.
      outputs: A list of output node(s) for the Graph.
code: def _get_metrics(self):
      metrics = {}
      for output_node in self.outputs:
          block = output_node.in_blocks[0]
          if isinstance(block, head_module.Head):
              metrics[block.name] = block.metrics
      return metrics
  
imports: import keras_tuner
  from tensorflow import keras
  from tensorflow import nest
  from autokeras import blocks
  from autokeras import keras_layers
  from autokeras import nodes
  from autokeras.engine import head
  from autokeras.engine import serializable
  from autokeras.utils import io_utils
label_desc: Use image node_id 10 for calling the Graph obj's underlying member method code with example usage: obj._get_metrics() and returns: metrics